1. Field of the Invention
The present invention relates to thermal transfer recording method and more particularly to an improved thermal transfer recording method of the type including ink ribbon which can be repeatedly used.
2. Description of the Prior Art
In the hitherto known facsimile apparatus, as means for receiving image informations of an original and recording them, electrostatic recording method and thermal transfer recording method are mainly employed for the signal receiving and recording mechanism. The electrostatic recording method has an advantageous feature that recording can be effected at a high speed with high image resolvability, but it has drawbacks that the apparatus using this method is complicated and expensive because developing and fixing of images are required. In addition, recording paper used in this apparatus is expensive, resulting in comparatively increased running cost. On the other hands, the thermal transfer recording method has advantageous features that developing and fixing of images are not required because the image is built by primary coloring under the effect of heating and an apparatus using this method can be constructed in the comparatively simple manner, but it has drawbacks that recording papers are of specially produced type which have less durability and the images recorded thereon can be falsified relatively easily.
In view of the problem inherent to the recording methods as described above, it has been proposed the thermal transfer recording apparatus for a facsimile equipment in which inexpensive ordinary paper is employed as recording medium. The thermal transfer recording apparatus of this type is operated such that recording paper made of ordinary paper and ink ribbon serving as master recording material and comprising a base film made of paper, plastic or the like material with a layer of thermally fusible solid ink containing coloring agent coated thereon are superimposed one above another so that the ink layer comes in contact with the recording paper and they are transported in a certain direction while the base film is depressed by means of a platen roller so as to allow it to come in contact with heating resistor elements of a thermal head. When pulse electric current is selectively caused to flow through the heating resistor elements in response to signals representing an image to be recorded, heat is generated at the heating resistor elements. The generated heat is transmitted to the solid ink layer through the base film of ink ribbon. Thus, the solid ink layer becomes in a semi-fused state a viscous. The semi-fused ink is transferred to recording paper under the influence of pressure given by the platen roller whereby a permanent image is built on the paper.
Since this type of recording apparatus uses ordinary paper as recording medium and does not require processes of developing and fixing, running cost can be reduced considerably and can be manufactured in a simple construction, in smaller dimensions and at an inexpensive cost. Further, since coloring agent having excellent weather proofness is used for the ink which is transferred only onto a required area on the paper, the recording paper and the recorded images are durable for a longer time and falsification of the recorded image is difficult to make compared with the foregoing heat sensitive recording apparatus.
However, it has been pointed out that the existent thermal transfer recording apparatuses fail to satisfactorily meet a variety of requirements for receiving and recording image signals, when used in a facsimile apparatus.
Generally, the conventional facsimile machine is adapted to handle originals having a variety of lengths and therefore the receiving apparatus is required to effect recording in which the recorded paper has the same length as that of the original. For the reason, it is preferable to use a roll of recording paper wound about a core as recording medium and automatically cut it off by the same length as that of an original by actuating an automatic cutter after completion of recording operation of received signal informations. However, in the case where the conventional thermal transfer recording system is applied to a receiving apparatus of a facsimile, sheet papers cut to a predetermined length, for instance, the length of A4 (29.7 cm) or B4 (36.4 cm) are usually used as recording medium, the length of an original of which image signal can be perfectly transmitted to the receiving apparatus is limited within the extent of the length of a single sheet paper or shorter than the length of the same. Further, the conventional facsimile receiving apparatus is constructed such that the length of ink ribbon is determined equal to the length of recording paper in the one-to-one relation. Therefore, when image informations of an original whose length is shorter than the length of a recording sheet paper are received by the facsimile receiving apparatus, both the ink ribbon and the recording paper are caused to have a blank area which is not concerned with recording. However, this is not preferable and acceptable from the viewpoint of cost and recording process. Another drawback of the conventional thermal transfer recording system is that recorded image is clearly kept on the ink ribbon in the form of a negative image after completion of recording operation. Therefore, there will arise a fear of leaking confidential informations from the used ink ribbon.